System for Converting Between Higher-Layer Packets and Lower-Layer Packets, A Method and A Base Station Server Thereof

ABSTRACT

The invention provides a system, method and base station server. According to an embodiment, a system for converting between higher-layer packets and lower-layer packets comprises a downlink base station server and an uplink base station client. The downlink base station server performs conversion of at least one downlink higher-layer packet to at least one downlink lower-layer packet by: receiving the at least one downlink higher-layer packet; converting the at least one downlink higher-layer packet to the at least one downlink lower-layer packet; and transmitting the at least one downlink lower-layer packet to a downlink base station client for transmission over a downlink channel to a downlink user device. The uplink base station client performs conversion of at least one uplink lower-layer packet to at least one uplink higher-layer packet and transmits the at least one uplink higher-layer packet to an uplink base station server.

RELATED APPLICATION

The application claims the priority date of U.S. Provisional PatentApplication No. 61/873,130 filed on 3 Sep. 2013, the disclosure of whichis incorporated herein by reference.

FIELD OF INVENTION

The present invention is generally (but not exclusively) related to asystem for converting between higher-layer packets and lower-layerpackets, a method thereof and a base station server.

BACKGROUND

In contrast to a conventional Third Generation Project Partnership(3GPP) Universal Mobile Telecommunications System (UMTS) system wherebase stations (Node B) are connected to each other via Radio NetworkControllers (RNC), the base stations (eNodeBs or eNBs) of a 3GPP LongTerm Evolution (LTE) system may be connected to one another directlywithout a RNC. However, conventional eNodeBs conforming to the 3GPP LTEstandard typically require significant upfront Capital Expenditure(CAPEX) (such as real estate costs for housing the Node B) and ongoingOperational Expenditure (OPEX) (such as energy costs for powering theNode B). Thus, there is a need for an improved or alternative system.

SUMMARY OF INVENTION

The present invention provides a system for converting betweenhigher-layer packets and lower-layer packets, comprising:

a downlink base station server performs a conversion of at least onedownlink higher-layer packet to at least one downlink lower-layerpacket; and

an uplink base station client performs a conversion of at least oneuplink lower-layer packet to at least one uplink higher-layer packet,

wherein the downlink base station server performs the conversion of theat least one downlink higher-layer packet to the at least one downlinklower-layer packet by:

receiving the at least one downlink higher-layer packet;

converting the at least one downlink higher-layer packet to the at leastone downlink lower-layer packet; and

transmitting the at least one downlink lower-layer packet to a downlinkbase station client for transmission over a downlink channel to adownlink user device, and

wherein the uplink base station client performs the conversion of the atleast one uplink lower-layer packet to the at least one uplinkhigher-layer packet by:

receiving the at least one uplink lower-layer packet over an uplinkchannel from an uplink user device;

converting the at least one uplink lower-layer packet to the at leastone uplink higher-layer packet; and

transmitting the at least one uplink higher-layer packet to an uplinkbase station server.

In an embodiment, the downlink base station server is located at a firstsite, and the uplink base station client is located at a second siteremote from the first site.

In an embodiment, the system further comprises the uplink base stationserver, wherein the downlink base station server and the uplink basestation server are implemented in the same device.

In an embodiment, the system further comprises the downlink base stationclient, wherein the downlink base station client and the uplink basestation client are implemented in the same device.

In an embodiment, the downlink channel is a downlink radio channel, andthe uplink channel is an uplink radio channel.

In an embodiment, the downlink base station server is connected to aplurality of downlink base station clients.

In an embodiment, the downlink base station server is connected to eachdownlink base station client via a respective one of a plurality ofdownlink optical fibre links.

In an embodiment, the downlink base station server is connected to eachdownlink base station client via a respective one of a plurality ofdownlink Ethernet connections.

In an embodiment, the uplink base station client is connected to theuplink base station server via an uplink optical fibre link.

In an embodiment, the uplink base station client is connected to theuplink base station server via an uplink Ethernet connection.

In an embodiment, each downlink higher-layer packet is a Service DataUnit (SDU) that conforms to the Third Generation Partnership Project(3GPP) Long Term Evolution (LTE) standard, each uplink higher-layerpacket is a SDU that conforms to the 3GPP LTE standard, each downlinklower-layer packet is a Packet Data Unit (PDU) that conforms to the 3GPPLTE standard, and each uplink lower-layer packet is a PDU that conformsto the 3GPP LTE standard.

In an embodiment, each downlink higher-layer packet corresponds to anInternet Protocol (IP) packet, and each uplink higher-layer packetcorresponds to an IP packet.

The present invention also provides a method of converting betweenhigher-layer packets and lower-layer packets, comprising:

performing a conversion of at least one downlink higher-layer packet toat least one downlink lower-layer packet at a downlink base stationserver; and

performing a conversion of at least one uplink lower-layer packet to atleast one uplink higher-layer packet at an uplink base station client,

wherein performing the conversion of the at least one downlinkhigher-layer packet to the at least one downlink lower-layer packet atthe downlink base station server comprises:

receiving the at least one downlink higher-layer packet;

converting the at least one downlink higher-layer packet to the at leastone downlink lower-layer packet; and

transmitting the at least one downlink lower-layer packet to a downlinkbase station client for transmission over a downlink channel to adownlink user device, and

wherein performing the conversion of the at least one uplink lower-layerpacket to the at least one uplink higher-layer packet at the uplink basestation client comprises:

receiving the at least one uplink lower-layer over an uplink channelfrom an uplink user device;

converting the at least one uplink lower-layer to the at least oneuplink higher-layer packet; and

transmitting the at least one uplink higher-layer packet to an uplinkbase station server.

In an embodiment, converting the at least one downlink higher-layerpacket to the at least one downlink lower-layer packet comprisessegmenting the at least one downlink higher-layer packet into aplurality of downlink lower-layer packets according to a Radio LinkControl (RLC) protocol.

In an embodiment, converting the at least one downlink higher-layerpacket to the at least one downlink lower-layer packet comprisesconcatenating a plurality of downlink higher-layer packets into the atleast one downlink lower-layer packet according to a Radio Link Control(RLC) protocol.

In an embodiment, converting the at least one downlink higher-layerpacket to the at least one downlink lower-layer packet comprisesreassembling the at least one downlink higher-layer packet as the atleast one downlink lower-layer packet according to a Radio Link Control(RLC) protocol.

In an embodiment, the Radio Link Control (RLC) protocol conforms to theThird Generation Partnership Project (3GPP) Long Term Evolution (LTE)standard.

The present invention also provides a base station server comprising:

at least one downlink packet transmitter, each downlink packettransmitter that:

receives at least one downlink higher-layer packet;

converts the at least one downlink higher-layer packet to at least onedownlink lower-layer packet; and

transmits the at least one downlink lower-layer packet to a downlinkbase station client for transmission over a downlink channel to adownlink user device; and

at least one uplink packet receiver, each uplink packet receiver that:

receives from an uplink base station client at least one uplinkhigher-layer packet converted by the uplink base station client from atleast one uplink lower-layer packet received by the uplink base stationclient over an uplink channel from an uplink user device; and

processes the at least one uplink higher-layer packet.

In an embodiment, the base station server comprises a plurality ofuplink packet receivers, each uplink packet receiver being associatedwith a respective one of the plurality of uplink base station clients.

In an embodiment, the base station server comprises a plurality ofdownlink packet transmitters, each downlink packet transmitter beingassociated with a respective one of the plurality of downlink basestation clients.

In an embodiment, the uplink packet receiver processes the at least oneuplink higher-layer packet, by transmitting the at least onehigher-layer packet to another one of the at least one downlink packettransmitter.

In an embodiment, the uplink packet receiver processes the at least oneuplink higher-layer packet, by transmitting the at least onehigher-layer packet to another base station server.

The present invention also provides a system for de-compressing packets,comprising:

a base station client performs a de-compression of a packet comprising aheader and a payload; and

a base station server further processes the de-compressed packet,

wherein the base station client performs the de-compression of thepacket by:

receiving the packet over a channel from a user device;

de-compressing the header of the packet; and

transmitting the de-compressed header and the payload of the packet asthe de-compressed packet to the base station server for furtherprocessing.

In an embodiment, the base station server is located at a first site,and the base station client is located at a second site remote from thefirst site.

In an embodiment, the channel is an uplink radio channel.

In an embodiment, the dez-compressed header is a header of an InternetProtocol (IP) packet.

In an embodiment, the header is a header of a Service Data Unit (SDU)that conforms to the Third Generation Partnership Project (3GPP) LongTerm Evolution (LTE) standard.

In an embodiment, the system further comprises a plurality of basestation clients, and wherein the base station server receives ade-compressed packet from each base station client.

In an embodiment, the base station server is connected to each basestation client via a respective one of a plurality of optical fibrelinks.

In an embodiment, the base station server is connected to each basestation client via a respective one of a plurality of Ethernetconnections.

The present invention also provides a method of de-compressing packets,comprising:

performing at a base station client a de-compression of a packetcomprising a header and a payload; and

further processing the de-compressed packet at a base station server,

wherein performing the de-compression of the packet at the base stationclient comprises:

receiving the packet over a channel from a user device;

de-compressing the header of the packet; and

transmitting the de-compressed header and the payload of the packet asthe de-compressed packet to the base station server for furtherprocessing.

In an embodiment, the header is de-compressed according to a Packet DataConvergence Protocol (PDCP).

In an embodiment, the Packet Data Convergence Protocol (PDCP) conformsto the Third Generation Partnership Project (3GPP) Long Term Evolution(LTE) standard.

The present invention also provides a base station server comprising:

at least one packet receiver, each packet receiver that:

receives from a base station client a packet de-compressed by the basestation client from a compressed packet received by the base stationclient over a channel from a user device; and

further processes the packet,

wherein the compressed packet comprises a compressed header and apayload, and the packet comprises a header de-compressed from the headerof the compressed packet and the payload of the compressed packet.

In an embodiment, the base station server comprises a plurality ofpacket receivers, each packet receiver being associated with arespective one of a plurality of base station clients.

In an embodiment, each packet receiver further processes the packet, bytransmitting the packet to another base station server.

In an embodiment, the base station server further comprises at least onedownlink packet transmitter, each downlink packet transmitter that:

receives a downlink packet comprising a header and a downlink payload;

compresses the header of the downlink packet; and

transmits the compressed header and the downlink payload of the downlinkpacket as the compressed downlink packet to a downlink base stationclient for transmission over a downlink channel to a downlink userdevice.

BRIEF DESCRIPTION OF DRAWINGS

In order that the invention may be more clearly ascertained, embodimentsof the invention will be described, by way of example, with reference tothe accompanying drawings in which:

FIG. 1 is a schematic diagram of an embodiment of the system comprisinga base station server and a plurality of base station clients;

FIG. 2 is a schematic diagram of the logical components of the system;

FIG. 3 is a schematic diagram of the physical components of the basestation server;

FIG. 4 is a schematic diagram of the physical components of a basestation client;

FIG. 5 is a schematic diagram of some of the functional components ofthe base station server and the base station client;

FIG. 6 is a flowchart of an embodiment of a method of operationperformed by the base station client of FIG. 5;

FIG. 7 is a flowchart of an embodiment of a method of operationperformed by the base station server of FIG. 5;

FIG. 8 is a schematic diagram of the other functional components of thebase station server and the functional components of the base stationclient;

FIG. 9 is a flowchart illustrating in greater detail the steps of FIG. 6performed by the base station client of FIG. 8;

FIG. 10 is a flowchart illustrating in greater detail the steps of FIG.7 performed by the base station server of FIG. 8;

FIG. 11 is schematic diagram of the other functional components of thebase station server of an alternative embodiment of the system, and thefunctional components of the base station client of the alternativeembodiment of the system;

FIG. 12 is a flowchart illustrating in greater detail the steps of FIG.6 performed by the base station client of the alternative embodiment ofthe system of FIG. 11;

FIG. 13 is a flowchart illustrating in greater detail the steps of FIG.7 performed by the base station server of the alternative embodiment ofthe system of FIG. 11;

FIGS. 14A and 14B are two flowcharts illustrating an embodiment of amethod performed by the base station client and the base station serverof the system; and

FIGS. 15A and 15B are two flowcharts illustrating, respectively, anembodiment of a method of compressing packets and an embodiment of amethod of decompressing packets.

DETAILED DESCRIPTION

Referring to the accompanying drawings, there is described a system 1,5, 111 for converting between higher-layer packets and lower-layerpackets, for example, between Radio Link Control (RLC) Service DataUnits (SDUs) and RLC Packet Data Units (PDUs) of the 3GPP LTE standard.The system 1, 5, 111 comprises a base station client 11 a, 12 a, 13 a,115 that receives uplink lower-layer packets from an uplink user devicesuch as an uplink User Equipment (UE) (that is, a UE making uplinktransmissions) conforming to the 3GPP LTE standard. The system 1, 5, 111also comprises a base station server 10 that receives downlinkhigh-layer packets for transmission to a downlink user device such as adownlink UE (that is, a UE making downlink transmissions). The basestation server 10 is performs a conversion of at least one downlinkhigher-layer packet to at least one downlink lower-layer packet, and thebase station client 11 a, 12 a, 13 a, 115 is performs a conversion of atleast one uplink lower-layer packet to at least one uplink higher-layerpacket. Thus, the system 1, 5, 111 is advantageous in that downlinkpacket conversions for multiple downlink UEs can be cost-effectivelycentralized at the base station server 10 without compromising theperformance (for example, delay or latency performance) of the system 1,5, 111 to perform uplink packet conversions for uplink UEs.

Persons skilled in the art will appreciate that the term “uplink” refersto the flow of data/packets from a UE to an eNodeB, and the term“downlink” refers to the flow of data/packets from an eNodeB to a UE.

Radio Protocol Architecture

The radio protocol architecture of the 3GPP LTE standard may beseparated into a user plane architecture (the user plane) and a controlplane architecture (the control plane). The user plane specifies radioprotocol layers (and radio protocol sub-layers) in respect of user data(or user traffic). The control plane specifies radio protocol layers(and radio protocol sub-layers) in respect of control/signallinginformation. The radio protocol layers (and radio protocol sub-layers)of the user plane architecture and the control plane architectureinclude:

Layer 1 (L1 layer)

-   -   Physical (PHY) sub-layer

Layer 2 (L2 layer)

-   -   Medium Access Control (MAC) sub-layer    -   Radio Link Control (RLC) sub-layer    -   Packet Data Convergence Protocol (PDCP) sub-layer

Layer 3 (L3 layer)

-   -   a Radio Resource Control (RRC) sub-layer

The operations that may be performed at the layers (and sub-layers) ofthe user plane and the control plane are specified in the 3GPP LTEstandard. For example, many of the operations performed by an eNodeB atthe layers (sub-layers) of the L2 layer may be found in TechnicalSpecification 36.300 of the 3GPP LTE standard.

General Construction of the System

FIG. 1 is a schematic diagram of an embodiment of the system 1. Thesystem 1 conforms to the 3GPP LTE standard, and is based on aCloud-Random Access Network (C-RAN) arrangement where basebandprocessing conventionally performed by a conventional eNodeB issplit/distributed between a base station server 10 (also referred to asa base station hotel) and a base station client 11 a, 12 a, 13 a (alsoreferred to as cell site equipment or a Remote Radio Head Unit (RHU)).

The system 1 comprises a base station server 10 and three base stationclients 11 a, 12 a, 13 a. Persons skilled in the art will appreciatethat the system 1 may include more than one base station server 10and/or one, two or more than three base station clients 11 a, 12 a, 13a.

Each base station client 11 a, 12 a, 13 a is located at a respective oneof a plurality of cell sites (or antenna towers) 11 b, 12 b, 13 blocated remotely from the location of the base station server 10, and isconnected to the base station server 10 such that one or more packets(for example, one or more RLC SDUs received from a UE) may betransmitted from the base station client 11 a, 12 a, 13 a to anotherbase station client 11 a, 12 a, 13 a via the base station server 10.Each base station client 11 a, 12 a, 13 a is connected to the basestation server 10 via an optical fibre link. Persons skilled in the artwill appreciate that one or more of the base station clients 11 a, 12 a,13 a may alternatively be connected to the base station server 10 via adifferent type of link such as a high-speed wireless link.

It is envisaged that the base station server 10 may be connected toother base station servers or conventional eNodeBs such that one or morepackets (for example, one or more RLC SDUs received from a base stationclient 11 a, 12 a, 13 a) may be transmitted from the base station server10 to another base station server or conventional eNodeB. The basestation server 10 may be connected to other base station servers orconventional eNodeBs via a core network (such as an Evolved Packet Core(EPC)), and that the base station server 10 may be connected to the corenetwork via a connection point (such as a General Packet Radio Service(GPRS) Tunnelling Protocol-User plane (GTP-U) Tunnel end point) at thecore network. Also, it is envisaged that the system 1 may supportmultiple bands and be scaled by increasing the number of base stationclients 11 a, 12 a, 13 a and the capacity of the base station server 10,for example, by increasing the number of baseband processing unitsimplemented by the base station server 10.

FIG. 2 is a schematic diagram of the logical components of the system 1.The base station server 10 comprises a plurality of clusters of Basebandprocessing Units (BBUs) 21. The BBUs 21 of each cluster of BBUs areconnected to a respective cluster packet scheduler 22. Each clusterpacket scheduler 22 can control each of the BBUs 21 connected to thecluster packet scheduler 22 to coordinate and/or manage packetscheduling and/or resource allocations. Also, the BBUs 21 of eachcluster of BBUs may be jointly coordinated by a corresponding clusterpacket scheduler 22.

In this embodiment, the base band server 10 is implemented on a VirtualCloud Platform (VCP), and each cluster packet scheduler 22 is connectedto a VCP packet scheduler 23. All of the BBUs of the system 1 may bejointly coordinated by the VCP packet scheduler 23. Each BBU 21 isconnected to a corresponding base station client 11 a, 12 a, 13 a via acorresponding cluster packet scheduler 22, and the VCP packet scheduler23.

Each BBU 21 comprises a RRC processing entity 211, a PDCP processingentity 212 and a RLC processing entity 213. Each BBU 21 is associatedwith a corresponding MAC/PHY processing entity 214. It is envisaged thatthe baseband processing conventionally performed by a conventionaleNodeB can be performed by a base station client 11 a, 12 a, 13 a, acorresponding BBU 21, a corresponding cluster packet scheduler 22, acorresponding MAC/PHY processing entity 214 and the VCP packet scheduler23 of the system 1.

FIG. 3 is a schematic diagram of the physical components of the VCP 3implementing the base station server 10. The VCP 3 includes a processorunit 31, a memory unit 32, an input/output interface 33 and a powermanagement unit 34. The processor unit 31 is logically or electricallyconnected to the memory unit 32, the input/output interface 33 and thepower management unit 34. It is envisaged that the VCP 3 may be a bladeserver, and the processor unit 31 may be a multi-core processor. Thememory unit 32 may include static memory storage devices and dynamicmemory storage devices.

The processor unit 31 is configured to implement (or execute) a numberof software modules based on program code and/or data stored in thememory unit 32. For example, the memory unit 32 stores program code forimplementing software modules corresponding to the RRC processing entity211, the PDCP processing entity 212, the RLC processing entity 213, theMAC/PHY processing 214, the cluster packet scheduler 22 and the VCPpacket scheduler entity 23. Persons skilled in the art will appreciatethat one or more of the software modules could alternatively beimplemented in some other way, for example, by one or more dedicatedcircuits.

The input/output interface 33 is an interface for connecting each BBU 21to a corresponding base station client 11 a, 12 a, 13 a. The powermanagement unit 34 includes a power supply (not shown) for providingelectrical power to the VCP 3 and management logics (not shown) forcontrolling the supply of power to the VCP 3.

FIG. 4 is a schematic diagram of the physical components of a basestation client 11 a, 12 a, 13 a. Each base station client 11 a, 12 a, 13a includes a processor unit 41, a memory unit 42, an input/outputinterface 43, a power management unit 44, and a Remote Radio Head (RRH)45. The RRH 45 comprises Radio Frequency (RF) circuitry for transmittingand/or receiving RF signals conforming to the 3GPP LTE standard. It isenvisaged that the RRH 45 may include an antenna (not shown) and RFsignal processing components (not shown) such as, but not limited to, aDigital-to-Analogue signal converter (DAC), an Analogue-to-Digitalsignal converter (ADC), an oscillation signal generator, a modulator, ademodulator, a power amplifier, and a bandpass filter.

The processor unit 41 is logically or electrically connected to thememory unit 42, the input/output interface 43, the power management unit44, and the RRH 45. It is envisaged that the processor unit 41 may be amulti-core processor. The memory unit 42 may include static memorystorage devices and dynamic memory storage devices. The processor unit41 is configured to implement (or execute) a number of software modulesbased on program code and/or data stored in the memory unit 42. Forexample, the memory unit 42 may store program code for implementingsoftware modules corresponding to a MAC/PHY processing entitycorresponding to the MAC/PHY processing entity 214 of FIG. 2. Personsskilled in the art will appreciate that one or more of the softwaremodules could alternatively be implemented in some other way, forexample, by one or more dedicated circuits.

The input/output interface 43 is an interface for connecting the basestation client 11 a, 12 a, 13 a to the base station server 10. The powermanagement unit 44 includes a power supply (not shown) for supplyingelectrical power to the base station client 11 a, 12 a, 13 a andmanagement logics (not shown) for controlling the electrical powersupply to the base station client 11 a, 12 a, 13 a.

Further Details of the System

FIG. 5 is a schematic diagram of the functional components (sharedfunctional components) implemented on the VCP 3 to manage the BBUs 21 ofthe base station server 10. In FIG. 5, only part 5 of the system 1 (morespecifically, only two of the BBUs 541, 551 and two of the base stationclients 11 a, 12 a) is illustrated. In FIG. 5, the baseband processingconventionally performed by a conventional eNodeB is performed by aneNodeB 54, 55 comprising a BBU 541 and a corresponding base stationclient 11 a, 12 a.

The VCP 3 comprises a carrier Ethernet Internet Protocol (IP) interfacein the form of a Giga-bit Ethernet interface 53. Each BBU 541, 551 isconnected to a corresponding base station client 11 a, 12 a via theGiga-bit Ethernet interface 53 and a Giga-bit Ethernet interface 401,552 of the base station client 11 a, 12 a.

The VCP 3 also includes a Radio Resource Management (RRM) entity 52including: a measurement control entity 521, a radio bearer admissioncontrol entity 522, a load balancing entity 523, a mobility controlentity 524, a radio bearer control entity 525, a Self-Organizing Network(SON) entity 526 and a cell coordination scheduler 527. Each BBU 541,551 is connected to the measurement control entity 521, the radio beareradmission control entity 522, the load balancing entity 523, themobility control entity 524, the radio bearer control entity 525 and theSON entity 526 via the cell coordination scheduler 527. The cellcoordination scheduler 527 performs radio resource allocation and packetscheduling for each BBU 541, 551 and corresponding base station client11 a, 12 a. The cell coordination scheduler 527 implements the clusterpacket scheduler 22 and the VCP packet scheduler 23 of FIG. 2.

The measurement control entity 521 controls broadcasting or transmissionof dedicated control/signalling information such that a UE in datacommunication with a BBU 541, 551 of the VCP 3 can, according to thecontrol/signalling information, perform measurements forintra/inter-frequency mobility. The radio bearer admission controlentity 522 determines whether a new radio bearer can be accepted by thesystem 1, 5, according to currently available radio resource (such asthe currently available radio resource of the serving cell base stationclient 11 a, 12 a). The load balancing entity 523 perform load balancingalgorithms (such as intra-frequency, inter-frequency or inter-RadioAccess Technology (RAT) algorithms for performing handovers). Themobility control entity 524 performs determinations related to mobilityof UEs, for example, during handover and Tracking Area Update (TAU). Theradio bearer control entity 525 establishes, maintains, and releasesradio bearers, and to configure radio resources associated with radiobearers. The SON entity 526 exchanges information (such as an AutomaticNeighbour Relation function) between neighbouring eNodeBs 54, 55. It isalso envisaged that the SON entity 526 may perform automatic PhysicalCell Identity (PCI) selection, dynamic configuration of X2/S1interfaces, Random Access Channel (RACH) parameter optimization, andmobility parameter optimization.

The VCP 3 also includes an Operation Administration Monitoring (OAM)entity 51. The OAM entity 51 is logically connected to the RRM entity52, each BBU 541, 551 and the Giga-bit Ethernet interface 53. The OAMentity 51 performs OAM/control operations. In particular, the OAM entity51 performs OAM/control of a MAC sub-layer processing entity (not shown)and a PHY sub-layer processing entity (not shown). It is envisaged thatsuch OAM/control typically involves relevant MAC and PHY sub-layersconfiguration information. It is envisaged that the OAM entity 51 mayinteract with the RRM entity 52 and directly transmit/receivecontrol/signalling information to/from a RRC sub-layer processing entity(not shown) of each BBU 541, 551. Also, the OAM entity 51 maytransmit/receive, over the Giga-bit Ethernet interface 53, OAM/controland configuration information to/from a corresponding OAM entity (notshown) of each base station client 11 a, 12 a.

FIG. 8 is a schematic diagram of the functional components of a BBU 541and a base station client 11 a of the embodiment of the system 1, 5 ofFIG. 5. In FIG. 8, some of the shared functional components (such as themeasurement control entity 521, the radio bearer admission controlentity 522, the load balancing entity 523, the mobility control entity524, the radio bearer control entity 525 and the SON entity 526 of theRRM 52) of the system 1, 5 are not shown.

The BBU 541 comprises a RRC processing entity 211, a PDCP processingentity 212, a RLC processing entity 213, and a MAC-Packet Scheduler(MAC-PS) processing entity 215. The RRC processing entity 211 islogically connected to the cell coordination scheduler 527 and the OAMentity 51 of the VCP 3. The RRC processing entity 211, the RLCprocessing entity 213 and the MAC-PS processing entity 215 are logicallyconnected to the base station client 11 a via the Giga-bit EthernetInterface 53 of the VCP 3.

The base station client 11 a comprises a security entity 403, a MACdownlink (DL) processing entity 404, a HARQ entity 405, a RLC processingentity 407, a PDCP processing entity 408, a PHY layer processing entity409, a RF unit 410, an antenna unit 411, an OAM processing entity 402and a MAC uplink (UL) processing entity 406. The MAC (DL) processingentity 404, the PHY processing entity 409, and the RF unit 410 arelogically connected to the OAM processing entity 402 of the base stationclient 11 a. The security entity 403 is logically connected to the RLCprocessing entity 213 of the BBU 541. The MAC (DL) processing entity 404is logically connected to the MAC-PS processing entity 215 of the BBU541. The PHY processing entity 409 is logically connected to the MAC-PSprocessing entity 215 of the BBU 541. The PDCP processing entity 408 islogically connected to the RRC processing entity 211 of the BBU 541.

The RRC processing entity 211 of the BBU 541 is responsible forperforming RRC sub-layer processing in both the uplink and the downlink.Persons skilled in the art will appreciate the RRC sub-layer processingmay include processing of control/signalling information in the controlplane and/or of data in the user plane.

The PHY layer processing entity 409, the RF unit 410 and the antennaunit 411 are responsible for performing PHY layer signal processing suchas RF signal processing in both the uplink and the downlink. Together,the PHY processing entity 409, the RF unit 410 and the antenna unit 411form the RRH 45 of FIG. 4.

The OAM processing entity 402 of the base station client 11 a passesOAM/control and configuration information to the MAC (DL) processingentity 404, the PHY processing entity 409, and the RF unit 410. It isenvisaged that OAM/control and configuration information may becommunicated between the OAM processing entity 51 of the VCP 3 and theOAM processing entity 402 of the base station client 11 a in both theuplink and the downlink.

PDCP, RLC and MAC sub-layer processing is split between the BBU 541 andthe base station client 11 a such that processing that is less latencycritical is performed by the BBU 541 and processing that is more latencycritical is performed by the base station client 11 a.

In the downlink, the PDCP processing entity 212, the RLC processingentity 213, and the MAC-PS processing entity 215 of the BBU 541 and theMAC (DL) processing entity 404 and the HARQ processing entity 405 of thebase station client 11 a are responsible for processingcontrol/signalling information in the control plane and/or data in theuser plane.

The PDCP processing entity 212 of the BBU 541 is responsible forperforming downlink PDCP sub-layer processing. For example, the PDCPprocessing entity 212 of the BBU 541 receives information on radiobearers, and map the information onto logical channels in the form of atleast one RLC PDU. In particular, the PDCP processing entity 212 of theBBU 541 receives one or more packets (such as Internet Protocol (IP)packets from, for example, a connection point at the core network),perform Robust Header Compression (ROHC) of the header of one or more ofthe received data packets, and transmit the compressed data packets tothe RLC processing entity of the BBU 541 for RLC sub-layer processing.

The RLC processing entity 213 of the BBU 541 is responsible forperforming downlink RLC sub-layer processing. More specifically, the RLCprocessing entity 213 of the BBU 541 performs a conversion of at leastone RLC SDU to at least one RLC PDU, by receiving the at least one RLCSDU from the PDCP processing entity 212, converting the at least one RLCSDU to at least one RLC PDU (for example, by segmenting a RLC SDU into aplurality of RLC PDUs or concatenating a plurality of RLC SDUs into oneRLC PDU), and transmitting the at least one RLC PDU to the base stationclient 11 a.

Downlink MAC sub-layer processing is performed by two separate parts ofa split downlink MAC processing entity comprising the MAC-PS processingentity 215 of the BBU 541 and the MAC downlink (DL) processing entity404 of the base station client 11 a. The MAC-PS processing entity 215 ofthe BBU 541 is responsible for determining downlink MAC sub-layerscheduling policies. In particular, the MAC-PS processing entity 215 ofthe BBU 541 generates, for each Transmission Time Interval (TTI),Resource Block (RB) resource allocations and a Control Format Indicator(CFI), and transmits the generated RB resource allocations and CFI tothe base station client 11 a. Scheduling control and coordinationinformation may be transmitted from the cell coordination scheduler 527of the BBU 541 to the MAC-PS processing entity 215 of the BBU 541.

The MAC (DL) processing entity 404 of the base station client 11 a isresponsible for performing (or implementing) the downlink MAC sub-layerscheduling policies determined by MAC-PS processing entity 215 of theBBU 541. For example, the MAC (DL) processing entity 404 of the basestation client 11 a controls transmissions or retransmissions of the atleast one RLC PDU from the RLC processing entity 213 based on the RBresource allocations and CFI generated by the MAC-PS processing entity215 of the BBU 541. That is, the MAC (DL) processing entity 404 controlsfor each TTI whether or not the base station client 11 a makes a new RLCPDU transmission or to send a retransmission of RLC PDU in the TTI. Itis envisaged that downlink MAC sub-layer processing is performed by theMAC (DL) processing entity 404 for all UEs within radio service coverageof the base station client 11 a.

The security entity 403 of the base station client 11 a is responsiblefor integrity of transmitted or received control/signalling informationin the control plane and/or data in the user plane. For example, thesecurity entity 403 encrypts the at least one RLC PDU generated by theRLC processing entity 213 of the BBU 541, before transmission orretransmission of the encrypted RLC PDU.

The HARQ processing entity 405 of the base station client 11 a isresponsible for informing the MAC (DL) processing entity 404 of the basestation client 11 a whether or not a transmission to a UE has beensuccessfully received by the UE in the downlink. In particular, the

HARQ processing entity 405 of the base station client 11 a transmits anyACK/NACK received from the UE to the MAC (DL) processing entity 404 ofthe base station client 11 a in the downlink. By implementing the HARQprocessing entity 405 together with the MAC (DL) processing entity 404and the PHY layer processing entity 409 at the base station client 11 a,it is expected that RLC PDUs requiring retransmission can beretransmitted directly from the base station client 11 a without firstbeing transmitted from the BBU 541 to the base station client 11 a.

It is envisaged that the HARQ processing entity 405 of the base stationclient 11 a may manage up to 8 HARQ processes per UE. Also, it isenvisaged that communications between the MAC (DL) processing entity 404and the HARQ processing entity 405 may include Downlink ControlInformation (DCI) related to Transport Blocks (TBs) to be transmitted toa UE in a TTI. Examples of DCI include HARQ process numbers and New DataIndicators (NDIs). Also, the DCI may alternatively or additionallyinclude Modulation and Coding Scheme (MCS) information, RedundancyVersion (RV) information, RB allocations information and/or antennamapping information for L1 layer coding and modulation.

Turning to the uplink, the HARQ processing entity 405, the MAC (UL)processing entity 406, the RLC processing entity 407, and the PDCPprocessing entity 408 of the base station client 11 a are responsiblefor processing control/signalling information in the control planeand/or data in the user plane.

The HARQ processing entity 405 of the base station client 11 a isresponsible for deriving one or more Transport Blocks (TBs) from RFsignals received by the PHY processing entity 409 of the base stationclient 11 a. The output of the HARQ processing entity 405 comprises TBswhich have been correctly received. Persons skilled in the art willappreciate that TBs may be received out of sequence by the base stationclient 11 a due to retransmissions. In addition to the correctlyreceived TBs, the HARQ processing entity 405 delivers Cyclic RedundancyChecks (CRCs) and ACKs/NACKs to the MAC (UL) processing entity 406 fortransmission to a UE. It is envisaged that such information may also beprovided to the MAC (DL) processing entity 404 for performing downlinkprocessing.

The MAC (UL) processing entity 406 of the base station client 11 agenerates at least one RLC PDU from the TBs output by the HARQprocessing entity 405 of the base station client 11 a. The MAC (UL)processing entity 406 of the base station client 11 a is also generatesinformation such as received CQI reports, acknowledgements(ACKs)/negative ACKs (NACKs), RACH Preambles, MAC control element (CE)information, and to transmit the generated information to the BBU 541.It is envisaged that the information may be generated independently bythe MAC (UL) processing entity 406 of the base station client 11 a ortogether in conjunction with the PHY processing entity 409 of the basestation client 11 a. It is envisaged that the RB resource allocationsand CFI generated for each TTI by the MAC-PS processing entity 215 ofthe BBU 541 may be based on at least part of the information generatedby the MAC (UL) processing entity 406 and the PHY processing entity 409of the BBU 541. Also,

The RLC processing entity 407 of the base station client 11 a isresponsible for performing uplink RLC sub-layer processing. Inparticular, the RLC processing entity 407 of the base station client 11a performs a conversion of the at least one RLC PDU generated by the MAC(UL) processing entity 406 of the base station client 11 a to at leastone RLC SDU, by receiving the at least one RLC PDU from the MAC (UL)processing entity 406, converting the at least one RLC PDU to at leastone RLC SDU (for example, by reassembling a plurality of RLC PDUs into aRLC SDU), and transmitting the at least one RLC SDU to the PDCPprocessing entity 408 of the base station client 11 a.

The PDCP processing entity 408 of the base station client 11 a isresponsible for performing uplink PDCP sub-layer processing. Inparticular, the PDCP processing entity 408 of the base station client 11a performs a de-compression of one or more of the SDUs received from theRLC processing entity 407 of the base station client 11 a, and toforward the SDU or SDUs (including those that are de-compressed by thePDCP processing entity 408) received from the RLC processing entity 407of the base station client 11 a to an appropriate entity. Morespecifically, the PDCP processing entity 408 de-compresses the header ofeach of the one or more SDUs according to ROHC (that is, the RobustHeader Compression framework), and forwards (i) the de-compressed headerof each one of the SDUs together with (ii) the corresponding payload tothe appropriate entity. It is envisaged that packets received from a UEin the user plane may be processed and then forwarded by the PDCPprocessing entity 408 of the base station client 11 a to an appropriateentity such as a connection point at the core network, and packetsreceived from a UE in the control plane may be forwarded by the PDCPprocessing entity 408 of the base station client 11 a to an appropriateentity such as the RRC processing entity 211 of the BBU 541.

FIG. 11 is schematic diagram of the functional components of the BBU 114and the base station client 115 of an alternative embodiment of thesystem 111. This alternative embodiment is almost the same as theembodiment of FIG. 8, except that encryption and decryption of RLC PDUsis performed by a PDCP processing entity 220 of the BBU 114 of thesystem 111 (as opposed to a separate security entity 403 at a basestation client 11 a in the embodiment of FIG. 8).

FIGS. 15A and 15B are two flowcharts 1500, 1502 illustratingrespectively an embodiment of a method of compressing packets, and anembodiment of a method of de-compressing packets. More specifically, theflowchart 1500 of FIG. 15A illustrates the steps to compress IP packetsreceived from a connection point at the core network in the downlink,and the flowchart 1502 of FIG. 15B illustrates the steps to de-compresscompressed IP packets received from the RLC processing entity 407 of thebase station client 11 a, 12 a, 13 a in the uplink.

Beginning first with the flowchart 1500 of FIG. 15A, in step 1520, thePDCP processing entity 212 implemented on the VCP 3 of the base stationserver 10 receives one or more IP packets from the connection point tothe core network. Each of the IP packets comprises an IP header and apayload.

In step 1560, the PDCP processing entity 212 performs downlink PDCPprocessing according to the PDCP protocol specified in the 3GPP LTEstandard. In particular, in step 1568, the PDCP processing entity 212compresses the IP header of each of one or more of the received IPpackets, according to the ROHC framework specified in the 3GPP LTEstandard.

In step 1580, the PDCP processing entity 212 transmits the compressedand uncompressed IP packets (that is, the received IP packets comprisingIP headers compressed by the PDCP processing entity 212, and thereceived IP packets comprising IP headers that are not compressed by thePDCP processing entity 212) to the RLC processing entity 213 implementedon the VCP 3 of the base station server 10 for further processing.

Turning to the flowchart 1502 of FIG. 15B, in step 1510, the PDCPprocessing entity 408 of the base station client 11 a, 12 a, 13 areceives one or more compressed IP packets. Each one of the compressedIP packet is a RLC SDU transmitted from an uplink user device to thebase station client 11 a, 12 a, 13 a over an uplink radio channelspecified in the 3GPP LTE standard. Each one of the compressed IP packetcomprises a compressed IP header and a payload.

In step 1530, the base station client 11 a, 12 a, 13 a performs uplinkPDCP processing on the compressed IP packets received from the uplinkuser device, according to the PDCP protocol specified in the 3GPP LTEstandard. In particular, the PDCP processing entity 408 de-compressesthe compressed IP header of each of the compressed IP packets in step1538.

In step 1590, the base station client 11 a, 12 a, 13 a transmits (i) theIP header (now de-compressed by the PDCP processing entity 408) of eachof the IP packets together with (ii) the corresponding payload to thebase station server 10 via the Giga-Bit Ethernet interface 401 of thebase station client 11 a, 12 a, 13 a for further processing (forexample, for the base station server 10 to transmit to the connectionpoint at the core network).

FIGS. 14A and 14B are two flowcharts 1400, 1402 illustrating anembodiment of a method of converting between RLC SDUs and RLC PDUsperformed by a base station client 11 a, 12 a, 13 a and a base stationserver 10 of the system 1, 5 of FIGS. 1 to 5 and 8. More specifically,the flowchart 1400 of FIG. 14A illustrates the steps performed by thebase station server 10 to perform a conversion of at least one RLC SDUto at least one RLC PDU in the downlink, and flowchart 1402 of FIG. 14Billustrates the steps performed by the base station client 11 a, 12 a 13a to perform a conversion of at least one RLC PDU to at least one RLCSDU in the uplink.

Beginning first with the flowchart 1400 of FIG. 14A, in step 1410, theRLC processing entity 213 implemented on the VCP 3 of the base stationserver 10 receives one or more RLC SDUs from the PDCP processing entity212 implemented on the VCP 3.

In step 1430, the RLC processing entity 213 converts the received RLCSDUs into one or more RLC PDUs according to the RLC protocol specifiedin the 3GPP LTE standard. For example, the RLC processing entity 213 mayconvert a received RLC SDU into a plurality of RLC PDUs, by segmentingthe received RLC SDU into the plurality of RLC PDUs in step 1433. Inanother example, the RLC processing entity 213 may convert a pluralityof received RLC SDUs into a RLC PDU, by concatenating the plurality ofreceived RLC SDUs into the RLC PDU in step 1439.

In step 1490, the RLC processing entity 213 transmits the RLC PDUs tothe base station client 11 a, 12 a, 13 a via the Giga-Bit Ethernetinterface 53 of the base station server 10 for transmission over a radiochannel to a UE in the downlink. Upon receiving the RLC PDUs from thebase station server 10, the base station client 11 a, 12 a, 13 a thentransmits the RLC PDUs over the radio channel to the UE. As indicatedabove, processing (such as encryption performed by the security entity403 of the base station client 11 a, 12 a, 13 a) of the RLC PDUs may beperformed by the base station client 11 a, 12 a, 13 a on the RLC PDUsreceived from the base station server 10, before the RLC PDUs istransmitted by base station client 11 a, 12 a, 13 a over the radiochannel to the UE.

Turning to the flowchart 1402 of FIG. 14B, in step 1420, the RLCprocessing entity 407 of the base station client 11 a, 12 a, 13 areceives one or more RLC PDUs from a UE via the MAC (UL) processingentity 406 and the PHY processing entity 409 of the base station client11 a, 12 a, 13 a.

In step 1460, the RLC processing entity 407 converts the received RLCPDUs into one or more RLC SDUs. More specifically, the RLC processingentity 407 converts the received RLC PDUs into the RLC SDUs, byreassembling the received RLC PDUs into the RLC SDUs according to theRLC protocol specified in the 3GPP LTE standard in step 1468.

In step 1480, the RLC processing entity 407 transmits the RLC SDUs tothe PDCP processing entity 408 of the base station client 11 a, 12 a, 13a for PDCP sub-layer processing (such as ROHC decompression), before theRLC SDUs is transmitted by the base station client 11 a, 12 a, 13 a tothe base station server 10 via the Giga-Bit Ethernet interface 401 ofthe base station client 11 a, 12 a, 13 a.

FIG. 6 is a flowchart of an embodiment of a method of operationperformed by a base station client 11 a, 12 a, 13 a of the embodiment ofthe system 1, 5 of FIG. 5.

In step S61, the base station client 11 a, 12 a, 13 a of the system 5performs the following steps in respect of the downlink: receiving oneor more RLC PDUs and radio resource scheduling information for a TTI ofa pre-configured duration over the Giga-Bit Ethernet interface 401, 552of the base station client 11 a, 12 a, 13 a from the VCP 3, convertingthe RLC PDUs into RF signals that are suitable for transmission to oneor more UEs according to the received radio resource schedulinginformation, and transmitting the RF signals to the one or more UEs. Theconversion of the RLC PDUs into the RF signals may include performingdownlink MAC sub-layer operations and downlink PHY sub-layer operations.

In step S62, the base station client 11 a, 12 a, 13 a performs thefollowing steps in respect of the uplink: receiving RF signals from oneor more UEs, transmitting information required for the MAC-PS processingentity 215 of the VCP 3 over the Giga-Bit Ethernet interface 401, 552 ofthe base station client 11 a, 12 a, 13 a, converting the received RFsignals into information on radio bearers, and transmitting theinformation on the radio bearers as packet signals over the Giga-BitEthernet interface 401, 552 to the VCP 3. The conversion of the receivedRF signals into the information on the radio bearers may includeperforming uplink MAC sub-layer operations, uplink RLC sub-layeroperations and uplink PDCP sub-layer operations.

Also, in step S63, an OAM entity of the base station client 11 atransmits/receives OAM/control and configuration information to/from acorresponding OAM entity 51 of the VCP 3 the uplink.

FIG. 7 is a flowchart of an embodiment of a method of operationperformed by a BBU 541, 551 of the system 5 of FIG. 5.

In step S71, the BBU 541, 551 performs the following steps in respect ofthe downlink: receiving, for one or more UEs under radio servicecoverage of a corresponding base station client 11 a, 12 a, 13 a,scheduling control and coordination information of the UEs from the cellcoordination scheduler 527.

In step S72, the BBU 541, 551 performs the following steps in respect ofthe downlink: receiving user-plane information on radio bearers over anetworking interface from a connection point at a core network,converting the user-plane information on radio bearers into one or moreRLC PDUs, and transmitting the RLC PDUs to a corresponding base stationclient 11 a, 12 a, 13 a over the Giga-Bit Ethernet interface 401, 552 ofthe VCP 3. The conversion of the user-plane information on radio bearersinto the RLC PDUs may include performing downlink PDCP sub-layeroperations and downlink RLC sub-layer operations.

In step S73, the BBU 541, 551 performs the following steps in respect ofthe downlink: generating, radio resource scheduling information for aTTI of a pre-configured duration, and transmitting the radio resourcescheduling information for the TTI to a corresponding base stationclient 11 a, 12 a, 13 a over the Giga-Bit Ethernet interface 401, 552 ofthe VCP 3.

In step S74, the BBU 541, 551 performs the following steps in respect ofthe downlink: receiving information required for MAC sub-layer downlinkscheduling from the corresponding base station client 11 a over theGiga-Bit Ethernet interface 401, 552 of the VCP 3.

In step S75, the BBU 541, 551 performs the following steps in respect ofthe downlink: receiving information on radio bearers as packet signalsfrom the corresponding base station client 11 a, 12 a, 13 a over theGiga-Bit Ethernet interface 401, 552 of the VCP 3.

In step S76, the OAM entity 51 of the VCP 3 transmits/receivesOAM/control and configuration information to/from corresponding OAMentities of the base station clients 11 a, 12 a, 13 a.

It is envisaged that the steps of the methods of operation illustratedin FIGS. 6 and 7 may be implemented by either the embodiment of thesystem 1, 5 shown in FIG. 8 or the alternative embodiment of the system1, 111 shown in FIG. 11.

FIG. 9 is a flowchart illustrating in greater detail the steps of theflowchart of FIG. 6 performed by the base station client 11 a, 12 a, 13a of the embodiment of the system 1, 5 of FIG. 8. More specifically,step S61 of FIG. 6 is illustrated in greater detail in steps S901 toS905 of FIG. 9, and step S62 of FIG. 6 is illustrated in greater detailin steps S906 to S913 of FIG. 9. That is, steps S901 to S905 describe ingreater detail the steps performed by the base station client 11 a inthe downlink, and steps S906 to S913 describe in greater detail thesteps performed by the base station client 11 a, 12 a, 13 a in theuplink.

In step S901, the base station client 11 a, 12 a, 13 a receives the RLCPDUs over the Giga-Bit Ethernet interface 401, 552 of the base stationclient 11 a, 12 a, 13 a from a corresponding BBU 541, 551.

In step S902, the base station client 11 a, 12 a, 13 a converts the RLCPDUs into information on logical channels. The conversion in step S902may include: performing a ciphering and integrity protection process onPDCP SDUs encapsulated in the RLC PDUs using the security entity 403 ofthe base station client 11 a, 12 a, 13 a. Conventionally, ciphering andintegrity protection of PDCP SDUs is performed by specialized hardwareimplemented by a conventional eNodeB to perform PDCP processing. In thisembodiment, ciphering and integrity protection is performed by thesecurity entity 403 of the base station client 11 a, 12 a, 13 a which isseparate to the PDCP processing entity 212 of the BBU 541, 551.

In step S903, the base station client 11 a, 12 a, 13 a receives RBresource allocations and a CFI for a TTI from the MAC-PS processingentity 215 of the BBU 541 over the Giga-bit Ethernet Interface 401 fromthe BBU 541, 551. It is envisaged that the MAC-PS processing entity 215may perform downlink MAC sub-layer packet scheduling operations andgenerate RB resource allocations and CFIs.

In step S904, the base station client 11 a, 12 a, 13 a converts theinformation on the logical channels into information on transportchannels according to the received RB resource allocations. Thisconversion is performed by the MAC (DL) processing entity 404 at thebase station client 11 a, 12 a, 13 a.

In step S905, the base station client 11 a converts the information onthe transport channels into RF signals suitable for transmission to theUEs. The conversion is performed by the PHY processing entity 409 of thebase station client 11 a. The RF signals are then transmitted to the UEsby the RF unit 410 and the antenna unit 411 of the base station client11 a, 12 a, 13 a.

Turning to steps S906 to S913 of FIG. 9, as indicated above, these stepscorrespond to step S62 of FIG. 6. That is, steps S906 to S913 describein greater detail the steps performed by the base station client 11 a inthe uplink.

In step S906, the base station client 11 a, 12 a, 13 a receives the RFsignals from the UEs.

In step S907, the base station client 11 a, 12 a, 13 a converts the RFsignals received from the UEs into information on transport channels.The conversion is executed by the PHY layer processing entity 409 of thebase station client 11 a, 12 a, 13 a.

In step S908, the base station client 11 a, 12 a, 13 a converts at leastsome of the information on the transport channels into packet signals.The information on the transport channels being converted may includereceived CQI reports, ACK/NACK, RACH preambles and MAC CE informationfrom the UEs.

In step S909, the base station client 11 a, 12 a, 13 a transmits thepacket signals obtained in step S908 to the MAC-PS processing entity 215of the BBU 541 over the Giga-bit Ethernet Interface 401.

In step S910, the MAC (UL) processing entity 406 of the base stationclient 11 a, 12 a, 13 a converts the rest of the information (that is,the rest of the information not converted in step S908) on the transportchannels into information on logical channels. It is envisaged that theMAC (UL) processing entity 406 may also be responsible for scheduling ofUEs in the uplink.

In step S911, the base station client 11 a, 12 a, 13 a converts theinformation on the logical channels into information on radio bearersusing the RLC processing entity 407 and the PDCP processing entity 408.The conversion includes: converting the information on the logicalchannels into PDCP SDUs; performing de-ciphering and integrityprotection on the PDCP SDUs; and converting the deciphered PDCP SDUsinto the corresponding information on radio bearers.

In step S912, the base station client 11 a, 12 a, 13 a determines theinformation on radio bearers and transmits the information on the radiobearers as packet signals over the Giga-bit Ethernet Interface 401 tothe BBU 541, 551. The information on the radio bearers may includepackets received in the uplink in the user plane, and packets receivedin the uplink in the control plane for RRC.

In step S913, the OAM entity 402 of the base station client 11 a, 12 a,13 a transmits/receives OAM/control and configuration informationto/from the OAM 51 at the VCP 3.

FIG. 10 is a flowchart illustrating in greater detail the steps of theflowchart of FIG. 7 performed by the base station server 10 of thesystem 1, 5 of FIG. 8. More specifically, step S72 of FIG. 7 isillustrated in greater detail in steps S1002 to S1003 of FIG. 10, andstep S73 of FIG. 6 is illustrated in greater detail in steps S1004 toS1005 of FIG. 10. That is, steps S1002 to S1003 describe in greaterdetail the steps performed the BBU 541, 551 in step S72 of FIG. 7 in thedownlink, and steps S1004 to S1005 describe in greater detail the stepsperformed by the base station client 11 a, 12 a, 13 a in step S73 ofFIG. 7 in the uplink.

In step S1001, the BBU 541, 551 receives scheduling control andcoordination information of the UEs within a cluster of cells/basestation clients 11 a, 12 a, 13 a from the cell coordination scheduler527.

In step S1002, the PDCP processing entity 212 of the BBU 541, 551receives information on radio bearers from a connection point at a corenetwork, and converts the information on radio bearers into informationon logical channels.

In step S1003, the RLC processing entity 213 of the BBU 541, 551converts the information on the logical channels into one or more RLCPDUs. Then, the BBU 541 transmits the RLC PDUs over the Giga-bitEthernet Interface 53 of the VCP 3 to the security entity 403 of thebase station client 11 a, 12 a, 13 a. As indicated above, ciphering andintegrity protection on the information on the logical channels isperformed by the security entity 403 of the base station client 11 a, 12a, 13 a.

Turning to steps S1004 to S1005 of FIG. 10, these steps correspond tostep S73 of FIG. 7. That is, steps S1004 to S1005 describe in greaterdetail the steps performed by the base station client 11 a, 12 a, 13 ain the uplink.

In step S1004, the MAC-PS processing entity 215 of the BBU 541, 551generates RB resource allocations and a CFI for UEs within radio servicecoverage for a TTI of a pre-configured duration. It is envisaged thatthe MAC-PS processing entity 215 may generate RB resource allocationsand a CFI based on scheduling control and coordination information ofUEs generated by the cell coordination scheduler 527.

In step S1005, the BBU 541, 551 transmits the RB resource allocationsand the CFI from the MAC-PS processing entity 215 over the Giga-bitEthernet Interface 53 of the VCP 3 to the base station client 11 a, 12a, 13 a.

In step S1006, the BBU 541, 551 receives from the base station client 11a, 12 a, 13 a packet signals containing information required for the MAC(DL) processing entity 404. The information required may include some ofthe information on the transport channels being converted at the basestation client 11 a, 12 a, 13 a, and may include received CQI reports,ACK/NACK, RACH preambles and MAC CE information from one or more UEs.

In step S1007, the VCP 3 receives information on radio bearers as packetsignals from the base station client 11 a, 12 a, 13 a over the Giga-bitEthernet Interface 53 of the VCP 3. More specifically, the RRCprocessing entity 211 of the BBU 541 receives packet signals in thecontrol plane for RRC packets in the uplink, and the connection point atthe core network receives packet signals in the user plane in the uplinkvia the VCP 3.

In step S1008, the OAM 51 of the VCP 3 transmits/receives OAM/controland configuration information to/from OAM entities 402 of the basestation client 11 a, 12 a, 13 a. The step S1008 may be performedsimultaneously along with the previously mentioned steps S1001 to S1007.

FIG. 12 is a flowchart illustrating in greater detail the steps of theflowchart of FIG. 6 performed by the base station client 115 of thealternative embodiment of the system 111 of FIG. 11. Most of the stepsof FIG. 12 correspond to the steps of FIG. 9. Specifically, steps S1201and S1203 to S1213 of FIG. 12 correspond to steps S901 and S903 to S913of FIG. 9. The difference between FIG. 12 and FIG. 9 is that cipheringand integrity protection on PDCP SDUs encapsulated in RLC PDUs isperformed by the security entity 403 of the base station client 11 a, 12a, 13 a in step S902 of FIG. 9, whereas ciphering and integrityprotection on PDCP SDUs encapsulated in RLC PDUs is not performed by thebase station client 115 in step S1202 of FIG. 12.

FIG. 13 is a flowchart illustrating in greater detail the steps of theflowchart of FIG. 7 performed by the alternative embodiment of thesystem 111 of FIG. 11. Most of the steps of FIG. 13 correspond to thesteps of FIG. 10. Specifically, steps S1301 and S1303 to S1308 of FIG.13 correspond to steps S1001 and S1003 to S1008 of FIG. 10. Thedifference between FIG. 13 and FIG. 10 is that ciphering and integrityprotection on PDCP SDUs encapsulated in RLC PDUs is performed by thePDCP processing entity 220 of the BBU 114 during conversion of theinformation on the radio bearers into the information on the logicalchannels in step S1302 of FIG. 13, whereas ciphering and integrityprotection on PDCP SDUs encapsulated in RLC PDUs is not performed by theBBU 541, 551 in step S1002 of FIG. 10.

Potential Advantages and/or Modifications in Report of the System

As indicated above, the functional components of the system 1, 5, 111 issplit between the BBU 541, 551, 114 and the base station client 11 a,115 such that processing that are more latency critical is performed bythe base station client 11 a, 12 a, 13 a, 115 (that is, at a cell sitewhere UEs are located), rather than the BBU 541, 551, 114. Thus, whencompared to a system where latency critical processing entities arecentralized at a location remote from cell sites, the system 1, 5, 111is advantageous in that it allows a reduction in data throughputrequirements (that is, the required amount of data throughput) betweenthe centralized base station server 10 and the remote base stationclients 11 a, 12 a, 13 a, 115.

Also, by centralizing some of the baseband processing performed by aconventional eNodeB at a single base station server 10, the system 1, 5,111 advantageously allows efficient and dynamic usage of processingpower which is otherwise distributed monolithically at multipleconventional eNodeBs. This may also lead to significant cost savings toeNodeB operators in terms of reduced CAPEX and OPEX due to a reductionin the number of cell sites.

Also, by performing PHY layer Digital Signal Processing (DSP) and RFprocessing at the base station clients 11 a, 12 a, 13 a, 115, the system1, 5, 111 advantageously minimizes transmissions between the basestation clients 11 a, 12 a, 13 a, 115 and the base station server 10.

When compared to a system where all baseband processing is performed ata cloud-based baseband processor, the system 1, 5, 111 is advantageousin that the data rate required between the base station server 10 andeach base station client 11 a, 12 a, 13 a, 115 may be lower because PHYlayer processing is performed at the point of transmission (that is, bythe RRH 45 of the base station client 11 a, 12 a, 13 a, 115).

Assuming that some optical regeneration between the VCP 3 and basestation client 11 a, 12 a, 13 a, 115, the system 1, 5, 111 allows for amaximum cable distance of around 130 km (as PHY layer processing isperformed at the point of transmission by the RRH 45). Thus, whencompared to a system where all baseband processing is performed at acloud-based baseband processor, the system 1, 5, 111 is advantageous inthat it allows a significant separation range between the VCP 3 and eachbase station client 11 a, 12 a, 13 a, 115.

Also, when compared to a centralized system where HARQ processing iscentralized, the system 1, 5, 111 is advantageous in that HARQprocessing can be efficiently performed at each base station client 11a, 12 a, 13 a, 115.

Also, it is envisaged that the system 1, 5, 111 meets the criticaltiming requirement of a sub-frame time budget of 1 millisecond, astypically required for systems conforming to the 3GPP LTE standard.

Also, it is envisaged that the system 1, 5, 111 meets the criticaltiming requirement of less than 5 ms for one way packet delay in anunloaded network, as typically required for systems conforming to the3GPP LTE standard. For example, assuming that the delay for the opticalfibre link between the base station server 10 and a base station client11 a, 12 a, 13 a, 115 takes the following into account eNodeB processing(from PDCP sub-layer to L1 layer) of 0.8 ms, transmission and reception,TTI, UE processing time of 0.8 ms, and a maximum propagation delay of0.3 ms (assuming a 100 km cell distance), the one way delayT_(D)=T_(eNodeB)+T_(TTI)+T_(P)+T_(UE)=2.9 ms, where T_(D) denotes theone way delay, T_(eNodeB) denotes the eNodeB processing time, T_(P)denotes maximum propagation delay, and T_(UE) denotes the UE processingtime. Assuming that HARQ retransmissions occur every 8 ms with aprobability of 10% (for a non-loaded network), the maximum delayT_(max)=2.9+0.8=3.7 ms. This results in a one way delay time budget of1.3 ms which is smaller than the required one way packet delaylimitation of 5 ms. If we make the same assumptions, the maximum cabledistance between the base station server 10 and a base station client 11a, 12 a, 13 a, 115 is 250 km which is typically sufficient for wholecity coverage.

In the system 1, 5, 111, base station deployment density can beincreased by increasing the number of base station clients 11 a, 12 a,13 a, 115 without deployment of additional base station servers 10. Inaddition, as the base station server 10 centralizes all of the basebandprocessing power, significant OPEX and CAPEX savings can be achieved andupgrades may be more easily achievable.

In the system 1, 5, 111, centralized pooling of processing resource canbe exploited to provide significant benefits to operators ofwireless/mobile communication networks. This may lead to cost savings,gather energy efficiency, capacity improvement and improved loadbalancing. For example, by housing baseband processing in one centrallocation at the base station server 10, an operator of the system 1, 5,111 can benefit from centralized management and operation of the radionetwork. The centralized management and operation of the wireless/mobilecommunication network may provide operation and management cost savings,and allow an operator of the system 1, 5, 111 to avoid the difficulty infinding a suitable site required for conventional eNodeBs and thecontinual operating expense of renting the real estate, ensuring anadequate power supply, shielding from the environment and securing thelocation. In addition, base station clients 11 a, 12 a, 13 a, 115 aresignificantly less complex in terms of functionality, size and powerrequirements compared to conventional eNodeBs. Thus, expansion of thesystem 1, 5, 111 may be cheaper and faster.

Significant reduction in costs may be achieved because of the potentialenergy efficiency of the system 1, 5, 111. Centralizing basebandprocessing may reduce the cost of climate control and the otherauxiliary site power costs conventionally required of conventionaleNodeBs. In the system 1, 5, 111, small cells requiring low transmissionpower may be deployed. An important benefit of pooling all basebandprocessing in the system 1, 5, 111, is that there may be more efficientusage of resource based on load conditions. Processing resource can beallocated from areas which have lower capacity to those requiring highercapacity. For instance, the base station clients 11 a, 12 a, 13 a, 115can effectively be turned off overnight when there is no trafficactivity within the coverage area of the base station clients 11 a, 12a, 13 a, 115. Additionally, the network may become more adapted tonon-uniform traffic where processing load from a heavily loaded BBU 541,551, 114 may be transferred to other under-utilized BBUs 541, 551, 114of the base station server 10.

The centralized architecture of the system 1, 5, 111 can be exploited toimprove system capacity. For example, channel status information/channelquality information may be reported by active UEs throughout cellcoverage areas to the base station server 10 for utilization by cellcoordination scheduler 527 to improve system capacity. For instance,when the cell coordination scheduler 527 allocates radio resource forone cell, the cell coordination scheduler 527 can take into accountconditions in neighbouring cells as well as the currently serving cell.Also, the centralized architecture of the system 1, 5, 111 can beexploited to implement joint processing and scheduling to combatinter-cell interference (ICI).

Since baseband processing is centralized at the base station server 10,there is a potential for simplifying inter-eNodeB communication in thesystem 1, 5, 111. This allows consideration of multi-site reception andtransmission techniques. Multi-site reception of a packet from a UE atmultiple eNodeBs can enhance cell capacity. This may decrease the numberof required retransmissions. Also, joint scheduling or beamformingtechniques in the downlink may be used by the system 1, 5, 111, as BBUs541, 551, 114 are centralized at the base station server 10.

Centralizing baseband processing at the base station server 10 allowsglobal radio resource management (or joint radio resource management) tobe implemented in the system 1, 5, 111. For instance, centralized BBUs541, 551, 114 can more easily perform joint processing and scheduling tomitigate inter-cell interference (ICI) and thus improve spectralefficiency. It is envisaged that spectrum efficiency of UEs at celledges can be improved using global radio resource management strategiessuch as Dynamic Carrier Scheduling (CS), Dynamic Packet Scheduling (PS),Inter-Cell Interference Coordination (ICIC) and Power Control. Theglobal radio resource management may also be performed in multi-cellsconditions within a number of cells consisting in a cluster in a staticor semi-static way. Also, a subset of cells within a cluster cancooperate in transmission to any UE associated with the cluster (forinstance, cooperative transmission to the UE), and thus implementCoordinated Multi-Point (CoMP) transmission/reception. Therefore, BBUs541, 551, 114 at the VCP 3 can more easily resolve network dynamics,adopt flexible spectrum usage, and accommodate interference in thewireless/mobile communication network.

It will be understood to persons skilled in the art of the inventionthat many modifications may be made to the system 1, 5, 111 (inparticular, to the base station server 10 and/or one or more of the basestation clients 11 a, 12 a, 13 a, 115) without departing from the spiritand scope of the invention.

For example, additional improvements in uplink capacity may be achievedby performing cooperative scheduling/transmission techniques in the VCP3, the uplink of the eNodeB protocol stack can operate locally at thecell site and thus may be implemented completely in the base stationclient 11 a, 12 a, 13 a, 115. The following descriptions illustrate suchimplementation in more details.

In the system 1, 5, 111, BBUs 541, 551, 114 can work together in a largephysical baseband resource pool. Signalling, traffic data and channelstate information (CSI) of active UEs can be easily shared by BBUs 541,551, 114 within a cluster of the base station server 10. The centralizedarchitecture of the system 1, 5, 111 can be exploited to implement jointprocessing and scheduling to mitigate inter-cell interference (ICI) andimprove spectral efficiency. For example, as opposed to conventionalsystems, inter-cell interference co-ordination (ICIC) can be implementedunder the C-RAN infrastructure.

The system 1, 5, 111 may implement dynamic circuit switching to improveload balance and overall operational reliability (that is, failureprotection). The overall carrier resource utilization can be increasedby sharing baseband processing resources of multiple base stationservers 10. This sharing of resources may allow multiple users todynamically access the air interface. Also, dynamic packet switching maybe adopted to provide UEs with flexible spectrum usage, and resourcesmay be dynamically allocated according to interference and trafficvolume, to guarantee Quality of Service as well as to achieve highcapacity.

In respect of the user plane, the connection point (such as a GTP-UTunnel end point) at the core network may be implemented by the BBU 541,551, 114 of VCP 3 for the downlink. Optionally, the connection point maybe also implemented by the BBU 541, 551, 114 of the VCP 3 for theuplink. The system 1, 5, 111 can support Frequency Division Duplex (FDD)mode and Time Division Duplex (TDD) mode.

All base station clients 11 a, 12 a, 13 a, 115 may be synchronized usingGlobal Positioning System (GPS) clock time-base. The reference forsystem timing (for example, system frame number) may be at the basestation clients 11 a, 12 a, 13 a, 115. For events that occur on SingleFrequency Network (SFN) boundaries, such as handover commands or systeminformation broadcasts, the VCP 3 may maintain such time offsets to eachbase station client 11 a, 12 a, 13 a, 115.

In the downlink, ROHC may be fully implemented by the BBUs 541, 551, 114of the VCP 3. ROHC may be exploited to compress IP packet headers whenit is necessary. The system 1, 5, 111 may support the option ofoperating with no ciphering. Disabling of integrity protection may beoptional. Security operations may be implemented by the security entity403 of the base station client 11 a, 12 a, 13 a, 115. In the downlink, aPDCP SDU transmitted from the BBU 541, 551, 114 to the base stationclient 11 a, 12 a, 13 a, 115 may remain un-ciphered until it reaches thebase station client 11 a, 12 a, 13 a, 115. Accompanying a PDCP PDU andassociated with that PDCP PDU may be metadata containing the informationrequired to encrypt and integrity protect/integrity check the PDU at alater time. The Metadata may consist of PDCP PDU lengths and offsetswithin RLC PDU depending on the RLC headers sizes and Length Indicators.These offsets may be kept in the metadata as the data flows through theprotocol stack of an eNodeB. Segmented PDU may be taken into account intransmission across “the Split”. Additionally, regarding uplinktransmission on the PDCP sub-layer operations of an eNodeB, the uplinkPDCP may be fully implemented by the base station client 11 a, 12 a, 13a, 115.

In respect of the RLC sub-layer in the downlink, RLC processing may befully implemented in an eNodeB instance of the BBU 541, 551, 114 of theVCP 3. In the uplink, RLC processing may be fully implemented by thebase station client 11 a, 12 a, 13 a, 115.

In respect of the MAC sub-layer in the downlink, the MAC-PS processingentity 215 may be located at the BBU 541, 551, 114 of the VCP 3. TheMAC-PS processing entity 215 may be responsible for scheduling the radioresources specific for one base station client 11 a, 12 a, 13 a, 115 (orcell) among a limited number of UE per TTI. The MAC-PS processing entity215 may operate on a TTI basis while being controlled by the cellcoordination scheduler 527 of the VCP 3 and operating on a longer timebasis. The cell coordination scheduler 527 may be responsible forhigh-level scheduling across all UEs in a cell or in a sector such thatQuality of Service (QoS) and/or other metrics may be maintained for eachradio bearer. On the other hand, the cell coordination scheduler 527operates on a longer time-base compared to the MAC-PS processing entity215 of the base station client 11 a, 12 a, 13 a, 115 and may cover thesituation where the total number of active UE per cell is greater thanthe number of UE capable of being scheduled by the MAC. The rest ofdownlink MAC sub-layer operations may be performed by the base stationclient 11 a, 12 a, 13 a, 115.

The MAC (DL) processing entity 404 at the base station client 11 a, 12a, 13 a, 115 may additionally perform the following operations: DownlinkShared Channel (DL-SCH) data transfer (including HARQ and multiplexingin the downlink), Paging Channel (PCH) transmission, Broadcast Channel(BCH) transmission, Discontinuous Reception, and MAC Reconfiguration andMAC Reset. The MAC sub-layer may receive RLC PDU per bearer, per UE orper TTI from the RLC sub-layer. Relevant control information may bederived from the MAC (DL) processing entity 404. In order for latency tobe less than 5 ms (as required by the 3GPP LTE standard), propagationtime between the base station server and the base station client 11 a,12 a, 13 a, 115 may nominally be less than 1.3 ms. The propagation timemay be more dependent in local IP routing environment which is dependenton the IP service provider network and Service Level Agreements (SLAs).

In respect of the MAC sub-layer, RB allocations per UE per TTI may betransmitted to the MAC (DL) processing entity 404 of the base stationclient 11 a, 12 a, 13 a, 115. Also, CQI reports received from a UE on aPhysical Uplink Shared Channel (PUSCH) or a Physical Uplink CommonControl Channel (PUCCH) may be sent from the MAC (UL) processing entity406 and the PHY layer processing entity 409 at the base station client11 a, 12 a, 13 a, 115 to the MAC-PS processing entity 215 of the VCP 3.

In respect of the MAC sub-layer, the MAC-PS processing entity 215 at theVCP 3 may use information from all scheduled UEs in the cell to optimizepacket/radio resource scheduling for UEs taking channel conditions perUE into account. Downlink HARQ indications received from the UE may besent from the MAC (UL) processing entity 406 and the PHY layerprocessing entity 409 at the base station client 11 a, 12 a, 13 a, 115to the MAC-PS processing entity 215 of the VCP 3. The MAC-PS processingentity 21 may use such information for any retransmissions. For example,the MAC-PS processing entity 215 may not schedule a HARQ process from aUE in a TTI unless it knows the ACK/NACK status of the previoustransmission for that HARQ process for that UE.

In respect of the MAC sub-layer, Random Access preambles received fromUE in the RACH procedure may be sent to the MAC-PS processing entity 215of the VCP 3. The MAC-PS processing entity 215 of the VCP 3 may use thisinformation to perform scheduling in respect of Random Access ResponseMAC messages. The interface between the MAC (UL) processing entity 406of the base station client 11 a, 12 a, 13 a, 115 and the MAC-PSprocessing entity 215 of the VCP 3 may support sending information aboutthe MAC Control Elements (CE) in the MAC buffer to the MAC-PS processingentity 215. The MAC-PS processing entity 215 may use this information toperform scheduling in respect of MAC CE messages. The MAC-PS processingentity 215 may generate a CFI every TTI for transmission on the PhysicalCFI Channel (PCFICH).

DCI Formats 0, 1x, 2x, 3x may be supported by the system 1, 5, 111.Timing may be preserved over the base station server and the basestation client 11 a, 12 a, 13 a, 115 such that, for a UE or UE groupidentified by an Radio Network Temporary Identifier (RNTI), the DCItransmitted on the PDCCH in one TTI corresponds to the MAC Schedulingderived in the VCP 3 for the Downlink-Shared Channel (DL-SCH) TBtransmitted on the Physical Downlink Shared Channel (PDSCH) in the sameTTL

In respect of the DL-SCH, the Common Control Channel (CCCH), DedicatedControl Channel (DCCH) and Dedicated Traffic Channel (DTCH) may besupported. The MAC (DL) processing entity 404 of the base station client11 a, 12 a, 13 a, 115 may be responsible for mapping the BroadcastControl Channel (BCCH), CCCH, DCCH and DTCH onto the downlink sharedchannel (DL-SCH).

In respect of the BCH, BCCH may be supported. The MAC (DL) processingentity 404 of the base station client 11 a, 12 a, 13 a, 115 may beresponsible for mapping the BCCH onto BCH for transmission on thePhysical Broadcast Channel (PBCH).

In respect of the PCH, Paging Control Channel (PCCH) may be supported.The MAC (DL) processing entity 404 of the base station client 11 a, 12a, 13 a, 115 may be responsible for mapping the PCCH onto PCH fortransmission on the PDSCH. PCH TBs are associated with DCI which in turnare associated with a Paging Radio Network Temporary Identity (P-RNTI).

In respect of the Multicast Channel (MCH), Multicast Traffic Channel(MTCH) and Multicast Control Channel (MCCH) may be supported. The MAC(DL) processing entity 404 of the base station client 11 a, 12 a, 13 a,115 may be responsible for mapping the MTCH and MCCH onto the MulticastChannel (MCH).

In respect of the uplink, the MAC-PS processing entity 215 may beimplemented by the base station client 11 a, 12 a, 13 a, 115. The MAC(UL) processing entity 406 of the base station client 11 a, 12 a, 13 a,115 may support the Uplink Shared Channel (UL-SCH). The MAC (DL)processing entity 404 and/or the MAC (UL) processing entity 406 of thebase station client 11 a, 12 a, 13 a, 115 may support RACH.

In respect of the PHY layer, the PHY layer processing entity 409 may beimplemented by the base station client 11 a, 12 a, 13 a, 115. The PHYlayer processing entity 409 of the base station client 11 a, 12 a, 13 a,115 may support transmission of PBCH in the downlink. The PHY layerprocessing entity 409 of the base station client 11 a, 12 a, 13 a, 115may support transmission of PDSCH in the downlink. The PHY layerprocessing entity 409 of the base station client 11 a, 12 a, 13 a, 115may support reception of Physical Random Access Channel (PRACH), PUCCHand PUSCH in the uplink. The PHY layer processing entity 409 of the basestation client 11 a, 12 a, 13 a, 115 may support transmission ofPhysical Multicast Channel (PMCH) in the downlink. The CFI provided bythe MAC-PS processing entity 215 of the BBU 541 may be processed by thePHY layer processing entity 409 of the base station client 11 a onto onePCFICH for transmission in the cell. The DCI (per UE or per group of UEsprovided by the MAC-PS processing entity 215 may be processed by the PHYlayer processing entity 409 of the base station client 11 a, 12 a, 13 a,115 onto one PDCCH for each UE or UE group. The Physical Hybrid-ARQIndicator Channel (PHICH) may transmit ACK/NACK based on the receivedUL-SCH Block Error indication per UE. The ACK/NACK may be transmitted atthe correct timing according to synchronous HARQ operation in the UL.

The PHY layer processing entity 409 of the base station client 11 a, 12a, 13 a, 115 may be implemented on commercially available devices suchas off-the-shelf Small Cell System on a Chip (SoC) devices. Thesecommercially available devices may contain on-chip hardwareco-processors to implement Fast Fourier Transform (FFT) or turbo-codingalgorithms as well as encryption and integrity protection algorithms.The PHY layer processing entity 409 of the base station client 11 a, 12a, 13 a, 115 may cipher all Data Radio Bearer (DRBs) which may includedata in the user plane and Signaling Radio Bearers (SRBs) 1 and 2 whichmay include control/signalling information in the control plane. The PHYlayer processing entity 409 the base station client 11 a, 12 a, 13 a,115 may also perform integrity protection for control/signallinginformation in the control plane.

For dynamic operation, the MAC-PS processing entity 215 of the BBU 541,551, 114 may calculate the optimum CFI per TTI such that the lowestnumber of symbols used is sufficient to control the instantaneous datatransmission requirement for that TTI. For static operation, the MAC-PSprocessing entity 215 of the BBU 541, 551, 114 may set a CFI based onthe number of UE contexts in the cell such that for low UE numbers,CFI=1; for medium UE numbers CFI=2; and for high UE numbers, CFI=3.

In the downlink, the DCI may consist of downlink scheduling assignments,HARQ information and power control information per UE or UE group aswell as an RNTI identifying the UE or UE group. The downlink schedulingassignments may be an allocation of Radio Bearer resource which comesfrom the MAC (UL) processing entity 406 of the base station client. Thisallocation may consist of Allocation Type, RB Allocation, and ModulationCoding Scheme (MCS). The HARQ information may include: HARQ ProcessNumber, NDI, and RV. This HARQ information may be input to the HARQentity implemented by the base station client 11 a, 12 a, 13 a, 115. ForDCIO, input is required from the MAC (UL) processing entity 406 at thebase station client 11 a, 12 a, 13 a, 115 of the eNodeB corresponding toa Scheduling Grant given in response to a previous Scheduling Requestfrom the UE in the uplink. The Scheduling Grant may include the RBAllocation, MCS and RV information, and may also include power controlinformation. Additionally, the Grant may also include a CQI Requestallowing aperiodic channel status request.

Further aspects of the system 1, 5, 111 will be apparent from the abovedescription of the system 1, 5, 111. Persons skilled in the art willalso appreciate that any of the methods described above could beembodied in program code. The program code could be supplied in a numberof ways, for example on a tangible computer readable medium, such as adisc or a memory (for example, that could replace part of the memoryunit 32 of the VCP 3 or the memory unit 42 of a base station client 11a) or as a data signal (for example, by transmitting it from the basestation server 10).

It is to be understood that, if any prior art is referred to herein,such reference does not constitute an admission that the prior art formsa part of the common general knowledge in the art in any country.

In the claims which follow and in the preceding description of theinvention, except where the context requires otherwise due to expresslanguage or necessary implication, the word “comprise” or variationssuch as “comprises” or “comprising” is used in an inclusive sense, thatis to specify the presence of the stated features but not to precludethe presence or addition of further features in various embodiments ofthe invention.

1. A system for converting between higher-layer packets and lower-layerpackets, comprising: a downlink base station server performs aconversion of at least one downlink higher-layer packet to at least onedownlink lower-layer packet; and an uplink base station client performsa conversion of at least one uplink lower-layer packet to at least oneuplink higher-layer packet, wherein the downlink base station serverperforms the conversion of the at least one downlink higher-layer packetto the at least one downlink lower-layer packet by: receiving the atleast one downlink higher-layer packet; converting the at least onedownlink higher-layer packet to the at least one downlink lower-layerpacket; and transmitting the at least one downlink lower-layer packet toa downlink base station client for transmission over a downlink channelto a downlink user device, and wherein the uplink base station clientperforms the conversion of the at least one uplink lower-layer packet tothe at least one uplink higher-layer packet by: receiving the at leastone uplink lower-layer packet over an uplink channel from an uplink userdevice; converting the at least one uplink lower-layer packet to the atleast one uplink higher-layer packet; and transmitting the at least oneuplink higher-layer packet to an uplink base station server.
 2. A systemas claimed in claim 1, wherein the downlink base station server islocated at a first site, and the uplink base station client is locatedat a second site remote from the first site.
 3. A system as claimed inclaim 1, further comprising the uplink base station server, wherein thedownlink base station server and the uplink base station server areimplemented in the same device.
 4. A system as claimed in claim 1,further comprising the downlink base station client, wherein thedownlink base station client and the uplink base station client areimplemented in the same device.
 5. A system as claimed in claim 1,wherein the downlink channel is a downlink radio channel, and the uplinkchannel is an uplink radio channel.
 6. A system as claimed in claim 1,wherein the downlink base station server is connected to a plurality ofdownlink base station clients.
 7. A system as claimed in claim 6,wherein the downlink base station server is connected to each downlinkbase station client via a respective one of a plurality of downlinkoptical fibre links.
 8. A system as claimed in claim 6, wherein thedownlink base station server is connected to each downlink base stationclient via a respective one of a plurality of downlink Ethernetconnections.
 9. A system as claimed in claim 1, wherein the uplink basestation client is connected to the uplink base station server via anuplink optical fibre link.
 10. A system as claimed in claim 1, whereinthe uplink base station client is connected to the uplink base stationserver via an uplink Ethernet connection.
 11. A system as claimed inclaim 1, wherein: each downlink higher-layer packet is a Service DataUnit (SDU) that conforms to the Third Generation Partnership Project(3GPP) Long Term Evolution (LTE) standard, each uplink higher-layerpacket is a SDU that conforms to the 3GPP LTE standard, each downlinklower-layer packet is a Packet Data Unit (PDU) that conforms to the 3GPPLTE standard, and each uplink lower-layer packet is a PDU that conformsto the 3GPP LTE standard.
 12. A system as claimed in claim 1, whereineach downlink higher-layer packet corresponds to an Internet Protocol(IP) packet, and each uplink higher-layer packet corresponds to an IPpacket.
 13. A method of converting between higher-layer packets andlower-layer packets, comprising: performing a conversion of at least onedownlink higher-layer packet to at least one downlink lower-layer packetat a downlink base station server; and performing a conversion of atleast one uplink lower-layer packet to at least one uplink higher-layerpacket at an uplink base station client, wherein performing theconversion of the at least one downlink higher-layer packet to the atleast one downlink lower-layer packet at the downlink base stationserver comprises: receiving the at least one downlink higher-layerpacket; converting the at least one downlink higher-layer packet to theat least one downlink lower-layer packet; and transmitting the at leastone downlink lower-layer packet to a downlink base station client fortransmission over a downlink channel to a downlink user device, andwherein performing the conversion of the at least one uplink lower-layerpacket to the at least one uplink higher-layer packet at the uplink basestation client comprises: receiving the at least one uplink lower-layerover an uplink channel from an uplink user device; converting the atleast one uplink lower-layer to the at least one uplink higher-layerpacket; and transmitting the at least one uplink higher-layer packet toan uplink base station server.
 14. A method as claimed in claim 13,wherein converting the at least one downlink higher-layer packet to theat least one downlink lower-layer packet comprises segmenting the atleast one downlink higher-layer packet into a plurality of downlinklower-layer packets according to a Radio Link Control (RLC) protocol.15. A method as claimed in claim 13, wherein converting the at least onedownlink higher-layer packet to the at least one downlink lower-layerpacket comprises concatenating a plurality of downlink higher-layerpackets into the at least one downlink lower-layer packet according to aRadio Link Control (RLC) protocol.
 16. A method as claimed in claim 13,wherein converting the at least one downlink higher-layer packet to theat least one downlink lower-layer packet comprises reassembling the atleast one downlink higher-layer packet as the at least one downlinklower-layer packet according to a Radio Link Control (RLC) protocol. 17.A method as claimed in claim 13, wherein the Radio Link Control (RLC)protocol confot ms to the Third Generation Partnership Project (3GPP)Long Term Evolution (LTE) standard.
 18. A base station servercomprising: at least one downlink packet transmitter, each downlinkpacket transmitter that: receives at least one downlink higher-layerpacket; converts the at least one downlink higher-layer packet to atleast one downlink lower-layer packet; and transmits the at least onedownlink lower-layer packet to a downlink base station client fortransmission over a downlink channel to a downlink user device; and atleast one uplink packet receiver, each uplink packet receiver that:receives from an uplink base station client at least one uplinkhigher-layer packet converted by the uplink base station client from atleast one uplink lower-layer packet received by the uplink base stationclient over an uplink channel from an uplink user device; and processesthe at least one uplink higher-layer packet.
 19. A base station serveras claimed in claim 18, wherein the base station server comprises aplurality of uplink packet receivers, each uplink packet receiver beingassociated with a respective one of the plurality of uplink base stationclients.
 20. A base station server as claimed in claim 18, wherein thebase station server comprises a plurality of downlink packettransmitters, each downlink packet transmitter being associated with arespective one of the plurality of downlink base station clients.
 21. Abase station server as claimed in claim 18, wherein the uplink packetreceiver processes the at least one uplink higher-layer packet, bytransmitting the at least one higher-layer packet to another one of theat least one downlink packet transmitter.
 22. A base station server asclaimed in claim 18, wherein the uplink packet receiver processes the atleast one uplink higher-layer packet, by transmitting the at least onehigher-layer packet to another base station server.